1. Field of the Invention
The invention concerns a peripheral pump with an impeller comprising a center web continuous as far as the circumference and with one blade ring on each side thereof, further comprising a housing and a conveyance channel starting at a suction aperture and passing through at least one flow duct inside the housing and through impeller blade cells therein to a discharge orifice.
2. Description of Related Art
Contrary to rotary piston or rotary piston pumps, peripheral pumps operate dynamically. A rotating impeller in a pumping chamber transmits kinetic energy from the impeller to the liquid being conveyed, and this energy is converted substantially into pressure energy.
The expression peripheral pump applies to a pump comprising an impeller with bilateral blade rings with short blades separated by a central web and centrally supported in a closed, circular housing. The flow ducts oppositely located to each other on both sides and at the circumference of the impeller consist each of a bilateral side duct part and of the peripheral duct overlapping the outer diameter of the impeller. The flow duct extends almost over the entire area of the impeller and is interrupted between suction and pressure pipe stubs. Ordinarily its cross-section is constant. A narrow slot seals the impeller relative to the housing walls. The suction and pressure pipe stubs are directly connected to the beginning of the flow duct and to its end, whereby the water at the impeller outside enters and is discharged from the flow duct. In the known pumps of this type, all impeller blades are equidistant from each other.
Illustratively such a pump is described in U.S. Pat. No. 2,724,338.
Like all other dynamic machinery, peripheral pumps generate noise in operation. Depending on pump design, such noise is of a characteristic composition.
The main cause of the noise level generated in such pumps are the periodic pressure fluctuations produced by a strongly turbulent, non-stationary flow, in particular when the impeller blades rotate past the housing plate. The pump housing so driven and the connected pipes will then radiate this sound as acoustics into the environment.
Frequently such noises are whistlings, which while not necessary loud, nevertheless often are in a bothersome frequency range, especially when the pump is operating in a low-noise room where the personnel's hearing has adjusted itself to this low level.
Attempts already have been carried out to lower the noise generated by the propellers or impellers of air blowers, gas or steam turbines by irregularly arranging these blades on a shaft or disk. Illustratively reference is made to the British Pat. No. 2,046,360 and the U.S. Pat. Nos. 4,253,800 and 3,398,866. However these known designs concern propellers or impellers mostly with blades slanting relative to a radial chord and mounted either on one side on a disk or projecting clear off a hub. The operation of such known devices and the flow in them does differ significantly however from a peripheral pump's.